DNA probes for the
colicin V, traT, iss, and iu genes were used in this study of four representative ColV plasmids together with 200 Escherichia coli strains isolated from the stools of patients with
diarrhea and 146 E. coli strains isolated from the blood of patients with
bacteremia. The study indicated that the ColV plasmids are heterogeneous. Southern and colony hybridization analyses showed that in most of the
colicin V-producing intestinal E. coli strains, the
colicin V genes are located in the chromosome (14 of 16); in most of the
colicin V-producing E. coli strains isolated from the blood, they are located in plasmids (18 of 22). In both intestinal and blood E. coli isolates, the traT, iss, and
aerobactin receptor genes were present at similar frequencies, but the frequency of the
aerobactin synthesis genes was significantly different. The
aerobactin receptor gene was present in 25% of the intestinal E. coli strains that lack the
aerobactin synthesis gene. In the blood isolates, the
aerobactin synthesis and receptor genes were present at almost equal frequencies. Among the
colicin V-producing isolates, the iss, traT, and iu genes were present in 95.5, 86.4, and 90.9% of the blood isolates and in only 68.8, 43.8, and 81.3% of the intestinal isolates, respectively. The ColV plasmids from blood isolates that were tested for the presence of traT, iss, and iu genes were homogeneous and had DNA sequences that hybridized with each of the probes. On the other hand, the two intestinal strains containing ColV genes in a plasmid were heterogeneous in regard to the carriage of these genes. The presence of ColV is not restricted to specific O types.